1. Field of the Invention
The present invention relates to a fiber network system, particularly to a fiber sensing system with self-detection mechanism that is able to detect fiber network system and enhance overall transmission reliability of a network.
2. Description of the Related Art
In recent years, Fiber Bragg Grating (FBG) has become an important element in the field of optical sensing. Among the sensing system that using FBG primarily, the ability of providing diversified division multiplexing is one of most important characteristic for those sensing systems. FBG within the applications of division multiplexing includes wavelength-division multiplexing (WDM), space-division multiplexing (SDM), time-division multiplexing (TDM), code-division multiple access (CDMA), strength wavelength-division multiplexing and frequency-modulated continuous-wave (CW) multiplexing. Based on the existing division multiplexing technology and their ability to combine with each other, long range FBG sensing system can be easily manufactured. Therefore, how to enhance reliability and survivability of the FBG sensing system becomes an important issue recently. In general, network using architecture such as bus (in-line) topology, tree (star) topology and ring topology is unable to provide protection function to the sensing system. For instance, when a fault point appears on a fiber line with bus topology, the fiber sensor is no longer able to provide any sensing for any part of the fiber line after the fault point. In order to maintain the survivability of the FBG sensing system and operation of sensing mechanism to avoid the situation caused by environmental issue such as the fault point, it is essential to create a self-restored mechanism within the actual fiber sensing application.
In the paper “J. Lightwave Technol (2001), p 32” proposed by W. P. Lin, it mentioned a sensing architecture that combined the tree topology and the ring topology. Then in 2003, P. C. Peng added a self-restored mechanism to the sensing architecture mentioned above and the experiment result was proposed in the paper “IEEE Photon. Technol. Lett. vol. 15 (2003), p. 1270.” However, such self-restored mechanism for the sensing network requires an additional active component on every remote node (RN) of the network, making the topology of the whole fiber network more complex and also increases the manufacture cost of the network. If there is a simpler FBG multi-ring fiber sensing system that has an ability of self protection (restoration), it would be able to solve many problems when multi-ring architecture network encounters disconnection. Such self-restoration mechanism can be executed quickly and provide users with wider and higher range of reliability, thus decrease production and maintenance cost of the network.
To overcome the abovementioned problem, the present invention proposes a novel fiber sensing system with self-detection mechanism that is able to overcome the obstacles encountered by the prior arts.